An electronic throttle control system (ETC) for controlling the amount of air to an engine is well known. The throttle plate located in the throttle body assembly pivots in response to signals received from the engine control unit (ECU) to regulate the amount of air received by the intake manifold. The ECU disables the ETC when the ECU detects a potential ETC fault based on signals from throttle plate and/or accelerator pedal position sensors incorporated in the ETC. A throttle plate return spring is utilized to position the throttle plate in a default position when the ETC is disabled to allow just enough air to the engine so that the vehicle operator can limp home at a reduced vehicle speed.
Default throttle position variation can adversely affect the limp home driving performance. If the default throttle position is too far open, the vehicle may move faster than desired, and if the default throttle position is too far closed, the vehicle may not have enough power to climb hills. Prior art ETCs that have utilized a single return spring design have exhibited these undesirable limp home driving characteristics due to the excessive tolerance stack-up of the throttle assembly components and/or features that establish the throttle plate default position. Dual return spring designs have been suggested for reducing the amount of default position variation, but dual return spring designs are undesirable due to the associated increase in part costs and assembly complexity.